Assuming the manufacturing was done correctly, are there any I/O connections that would cause a 3V3 short?

[FAdar.1]

• The module that was used on this PCB was the STM32WB5MMG
• I/O was connected according to the datasheet attached for STM32WB55MMG
• Short found on 3V3 on 6 out of 6 sample prototypes. When module was desoldered from the PCB, the short went away on both PCB and module.
• Solder bridging was suspected. Post-mfg x-rays showed 3 possible solder bridges, with one of them on 3V3 pin. However, this one was bridged to an unconnected pin.
• SWDIO and SWCLK were already identified as incorrect connections. There are two schematic attachments, one for before and after this was changed the ECAD. The layout attachments are after the changes.

[TDK]

I assume you mean a short between 3V3 and GND. I don't think anything would explain that behavior other than a solder bridge or similar between 3V3 and GND, especially if the chip isn't even powered. If you resolder it to the board, does the short come back or stay away?

[FAdar.1]

Yes, short between 3V3 and GND. Batteries were connected after assembly, so there was current on 3V3 line. When chip was resoldered, the short went away on both board and chip.

[TDK]

> When chip was resoldered, the short went away on both board and chip.

I don't see what else would explain it other than a solder bridge. Given that the xray turned up 3 of them, seems plausible it may have missed some as well. Clearly there were manufacturing issues.

That's a cool xray reconstruction photo.